When a user requests a web page via a browser, the browser usually displays only part of the requested web page due to display size constraints. Especially for a mobile device that has a relatively small screen, a substantial portion of the requested web page may remain outside the initial visible area displayed by the browser. The user may or may not scroll down to the portion that is not displayed. If the browser renders the entire page but the user does not scroll down and view the entire page, processing resources are used unnecessarily.
Some browsers divide a content page into a plurality of tiles, each of which can be updated independently of the others. Tiles visible in the display area of the browser can be called on-screen tiles. Tiles outside the display area of the browser can be called off-screen tiles. User interactions, animations, script executions, and other types of events can cause the appearance of a page to change, in which case some of the tiles become “damaged.” Rather than updating the entire page, the browser may only update the damaged tiles. If off-screen tiles are updated but are not subsequently scrolled-to by the user, the processing resources used to update them are wasted. One known approach for addressing this problem is to determine whether to update the off-screen tiles based on their distances from the visible display area of the page.